JSON Validator

Validate JSON and pinpoint syntax errors.

Validate JSON against the strict RFC 8259 grammar and find the first syntax error by line and column, with a caret pointing at the exact character. Valid JSON is also shown nicely formatted. Runs fully in your browser — nothing is uploaded.

How to use JSON Validator

  1. Paste your JSON

    Paste your JSON or upload a .json file into this free online JSON validator to check it instantly in your browser, with nothing uploaded.

  2. Validate instantly

    The JSON validator parses your input against the strict RFC 8259 grammar and tells you immediately whether the JSON is valid, with no sign-up required.

  3. Locate the error

    If the JSON is broken, a red banner reports the exact line and column with a caret pointing at the offending character so you can find the problem fast.

  4. Fix common mistakes

    Correct trailing commas, missing quotes, single quotes or unbalanced brackets at the highlighted spot, then revalidate to confirm the JSON is well-formed.

  5. Format when valid

    When your JSON is valid, the right pane shows a tidy, indented, beautified copy, so this tool works as both a JSON validator and a JSON formatter.

  6. Copy or download

    Copy the clean, formatted JSON to your clipboard or download it as a ready-to-use .json file straight from your browser.

Frequently asked questions

What counts as valid JSON?

Strict JSON allows objects, arrays, strings (double-quoted), numbers, true, false and null. It does NOT allow comments, trailing commas, single quotes, unquoted keys, or values like NaN and Infinity. This validator follows that strict standard, the same one JSON.parse uses.

Where is the error in my JSON?

The red banner reports the line and column of the first problem and draws a caret (^) under the exact character in the offending line, so you can spot issues like a missing comma between array items immediately.

Can I validate a whole file?

Yes — click Upload and pick a .json file, or paste its contents. Everything is processed locally in your browser, so even large or confidential files never leave your machine.

Is this the same as JSON Schema validation?

No. This checks syntax (is it well-formed JSON?). JSON Schema validation checks that the data matches a defined structure/types. This tool focuses on fast, reliable syntax validation and formatting.

How do I validate JSON online for free?

Paste your JSON or upload a .json file into this free online JSON validator and it instantly checks whether the JSON is valid. If there’s a syntax error it pinpoints the exact line and column; if it’s valid, it returns a clean, formatted copy.

How do I fix “unexpected token” or “invalid JSON” errors?

Those errors usually mean a trailing comma, a missing comma or quote, single quotes instead of double quotes, or an unbalanced bracket. This JSON validator highlights the precise line, column and character so you can fix the broken JSON in seconds.

Can I use this as a JSON formatter and beautifier too?

Yes. Whenever your input is valid JSON, the right pane shows a tidy, indented, beautified version you can copy or download — so this tool works as both a JSON validator and a JSON formatter in one.

Why does my JSON fail because of a trailing comma?

Strict JSON doesn't allow a comma after the last item in an object or array — that's a common habit carried over from JavaScript, which is more lenient. The validator flags the exact spot; just remove the trailing comma and it will pass.

Can I validate JSON from an API response?

Yes. Paste the raw response straight from your browser's network tab, curl or Postman — the validator checks it against the strict JSON grammar and, if valid, shows a clean formatted copy so you can confirm the payload is correct.

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